Chiller system

ABSTRACT

A chiller system is provided. The chiller system may include a plurality of chillers, each of which may include a compressor, a condenser, and an evaporator, and a controller that controls the plurality of chillers. The controller may determine an expected load and a chiller to be operated of the plurality of chillers on the basis of the determined expected load to operate the determined chiller.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims priority under 35 U.S.C. 119 and 35 U.S.C. 365 to Korean Patent Application No. 10-2014-0109869, filed in Korea on Aug. 22, 2014, which is hereby incorporated by reference in its entirety.

BACKGROUND

1. Field

A chiller system is disclosed herein.

2. Background

In general, chillers supply cold water to cold water demand sources. In such a chiller, a refrigerant circulated in a refrigeration system and cold water circulated between a demand source and the refrigeration system may be heat-exchanged with each other to cool the cold water. The chiller may be high-capacity equipment, and thus, may be installed in large-scale buildings.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements, and wherein:

FIG. 1 is a view of a chiller system according to an embodiment;

FIG. 2 is a system view illustrating a chiller according to an embodiment;

FIG. 3 is a conceptive view of the chiller of FIG. 2;

FIG. 4 is a perspective view of a chiller set according to an embodiment;

FIG. 5 is a flowchart of a method of controlling the chiller set during an initial operation of the chiller set according to an embodiment;

FIG. 6 is a flowchart of a method of controlling the chiller set according to a variation in load during operation of the chiller set according to an embodiment; and

FIG. 7 is a graph illustrating a logarithmic control reference of the chiller according to a head factor and a load factor.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. Where possible, like reference numerals have been used to indicate like elements and repetitive disclosure has been omitted.

In the following detailed description of embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice, and it is understood that other embodiments may be utilized and that logical structural, mechanical, electrical, and chemical changes may be made without departing from the spirit or scope. To avoid detail not necessary to enable those skilled in the art to practice, the description may omit certain information known to those skilled in the art. The following detailed description is, therefore, not to be taken in a limiting sense.

Also, in the description of embodiments, terms such as first, second, A, B, (a), (b), for example, may be used herein when describing components. Each of these terminologies is not used to define an essence, order or sequence of a corresponding component but used merely to distinguish the corresponding component from other component(s). It should be noted that if it is described in the specification that one component is “connected,” “coupled” or “joined” to another component, the former may be directly “connected,” “coupled,” and “joined” to the latter or “connected”, “coupled”, and “joined” to the latter via another component.

FIG. 1 is a view of a chiller system according to an embodiment. FIG. 2 is a system view of a chiller according to an embodiment. FIG. 3 is a conceptive view of the chiller of FIG. 2.

Referring to FIGS. 1 to 3, a chiller system 10 according to an embodiment may include a chiller module or chiller 100, in which a refrigeration cycle may be performed, a cooling tower 20 that supplies cooling water into the chiller 100, and a cold water demand source 30, into which the cold water heat-exchanged with the chiller 100 may be circulated. The cold water demand source 30 may be, for example, a device or space for conditioning air using cold water.

A cooling water circulation passage 40 may be disposed between the chiller 100 and the cooling tower 20. The cooling water circulation passage 40 may include a tube that guides the cooling water so that the cooling water may be circulated into the cooling tower 20 and a condenser 120 of the chiller 100. The cooling water circulation passage 40 may include a cooling water inflow passage 42 that guides the cooling water so that the cooling water may be introduced into the condenser 120, and a cooling water outflow passage 44 that guides the cooling water heated in the condenser 120 to flow into the cooling tower 20.

A cooling water pump 46 that operates to allow the cooling water to flow may be disposed in at least one passage of the cooling water inflow passage 42 or the cooling water outflow passage 44. For example, in FIG. 1, the cooling water pump 46 is disposed in the cooling water inflow passage 42.

A cooling water outflow temperature sensor 47 to detect a temperature of the cooling water introduced into the cooling tower 20 may be disposed in the cooling water outflow passage 44. A cooling water inflow temperature sensor 48 to detect a temperature of the cooling water discharged from the cooling tower 20 may be disposed in the cooling water inflow passage 42.

A cold water circulation passage 50 may be disposed between the chiller 100 and the cold water demand source 30. The cold water circulation passage 50 may include a tube that guides the cold water so that the cold water may be circulated into the cold water demand source 30, and an evaporator 140 of the chiller 100.

The cold water circulation passage may include a cold water inflow passage 52 that guides the cold water so that the cold water may be introduced into the evaporator 140, and a cold water outflow passage 54 that guides the cold water cooled in the evaporator 140 to flow into the cold water demand source 30.

A cold water pump 56 that operates to allow the cold water to flow may be disposed in at least one passage of the cold water inflow passage 52 or the cold water outflow passage 54. For example, in FIG. 1, the cold water pump 56 is disposed in the cold water inflow passage 52.

A cold water inflow temperature sensor 53 to detect a temperature of the cold water introduced into the chiller 100 may be disposed in the cold water inflow passage 52, and a cold water outflow temperature sensor 55 to detect a temperature of the cold water discharged from the chiller 100 may be disposed in the cold water outflow passage 54. Alternatively, the cold water inflow temperature sensor 53 and the cold water outflow temperature sensor 55 may be disposed in the chiller module 100.

The cold water demand source 30 may be a water cooling type air-conditioner , in which air and cold water may be heat-exchanged with each other. For example, the cold water demand source 30 may include at least one unit or device of an air handling unit (AHU) or an handler, in which indoor air and outdoor air are mixed with each other, and the mixed air is heat-exchanged with cold water to discharge the cooled air into an indoor space, a fan coil unit (FCU) or fan coil disposed in the indoor space to heat-exchange the indoor air with the cold water, and thereby discharge the cooled air into the indoor space, and a bottom tube unit or bottom tube buried in the bottom of the indoor space.

For example, in FIG. 1, the cold water demand source 30 is provided as the AHU. In detail, the AHU may include a casing 61, a cold water coil 62 disposed in the casing 61 to allow the cold water to pass therethrough, and blowers 63 and 64 disposed on both sides of the cold water coil 62 to suction the indoor air and outdoor air, thereby blowing the indoor and outdoor air into the indoor space.

The blowers 63 and 64 may include a first blower 63 to suction the indoor and outdoor air into the casing 61, and a second blower 64 to discharge conditioned air outside of the casing 61. The casing 61 may include an indoor air suction inlet 65, an indoor air discharge outlet 66, an external air suction inlet 67, and a conditioned air discharge outlet 68.

When the blowers 63 and 64 are driven, a portion or first portion of the air suctioned in from the indoor space through the indoor air suction inlet 65 may be discharged through the indoor air discharge outlet 66, and the remaining portion or a second portion not discharged through the indoor air discharge outlet 66 may be mixed with the outdoor air suctioned in through the external suction outlet 67, and then, may be heat-exchanged with the cold water coil 62. Also, the mixed air heat-exchanged (cooled) with the cold water coil 62 may be discharged into the indoor space through the conditioned air discharge outlet 68.

The chiller 100 may include a compressor 110 that compresses the refrigerant, the condenser 120, into which the high-temperature, high-pressure compressed in the compressor 110 may be introduced, expansion devices 131 and 132 that decompress the refrigerant condensed in the condenser 120, and the evaporator 140 that evaporates the refrigerant decompressed in the expansion devices 131 and 132. The expansion devices 131 and 132 may include a first expansion device 131 to primarily expand the refrigerant discharged from the condenser 120, and a second expansion device 132 to secondarily expand the refrigerant separated in the economizer 150.

The chiller 100 may further include a suction tube 101 disposed on or at an inlet-side of the compressor 110 to guide the refrigerant discharged from the evaporator 140 into the compressor 110, and a discharge tube 102 disposed on or at an outlet-side of the compressor 110 to guide the refrigerant discharged from the compressor 110 into the condenser 120. An oil collection tube 108 that guides oil in the evaporator 140 into the suction-side of the compressor 110 may be disposed between the evaporator 140 and the compressor 110.

The compressor 110 may include an impeller to compress the refrigerant. The compressor 110 may further include a motor 112 to drive the impeller 111. The compressor 110 may include at least one gear to transmit a drive force of the motor 112 to the impeller 111.

The compressor 110 may also include a guide vane 114 to adjust an amount of refrigerant introduced into and discharged from the impeller 111. That is, the guide vane 114 may adjust an opening degree of a flow path of the refrigerant, and thus, a flow rate of the refrigerant may be adjusted according to the opening degree. For example, if the guide vane 114 increases in opening degree, the flow rate of the refrigerant may increase. On the other hand, if the guide vane 114 decreases in opening degree, the flow rate of the refrigerant may decrease. Each of the condenser 120 and the evaporator 140 may be provided as a shell and tube type heat-exchanger so that the refrigerant and the water may be heat-exchanged with each other.

In detail, the condenser 120 may include a shell 121 that defines an exterior thereof, a refrigerant inflow hole 122 disposed in or at one or a first side of the shell 121 to introduce the refrigerant compressed in the compressor 110 therethrough, and a refrigerant outflow hole 123 defined in or at the other or a second side of the shell 121 to discharge the refrigerant condensed in the condenser 120 therethrough.

The condenser 120 may further include a cooling water tube array 124 disposed in the shell 121 to guide a flow of the cooling water, a cooling water inflow inlet 125 disposed on or at an end of the shell 121 to introduce the cooling water into the cooling water tube assembly 124, and a cooling water outflow outlet 126 disposed on or at the end or another end of the shell 121 to discharge the cooling water from the cooling water tube array 124. The cooling water inflow inlet 125 may be connected to the cooling water inflow passage 42, and the cooling water outflow outlet 126 may be connected to the cooling water outflow passage 44.

An economizer 150 may be disposed on the refrigerant outlet-side of the condenser 120. The first expansion device 131 may be disposed on or at an inlet-side of the economizer 150. The refrigerant condensed in the condenser 120 may be introduced into the economizer 150 after being primarily decompressed in the first expansion device 131.

A liquid refrigerant and a gaseous refrigerant of the primarily decompressed refrigerant may be separated from each other by the economizer 150. The separated gaseous refrigerant may be introduced into the compressor 110, and the separated liquid refrigerant may be introduced into the second expansion device 132 and then, may be secondarily decompressed.

The evaporator 140 may include a shell 141 that defines an exterior thereof, a refrigerant inflow hole 142 disposed in or at one or a first side of the shell 141 to introduce the refrigerant expanded in the second expansion device 132 therethrough, and a refrigerant outflow hole 143 defined in or at the other or a second side of the shell 141 to discharge the refrigerant evaporated in the evaporator 140 therethrough. The refrigerant outflow hole 143 may be connected to the suction tube 101. The evaporator 140 may further include a cold water tube array 144 disposed in the shell 141 to guide a flow of the cold water, a cold water inflow inlet 145 disposed on or at an end of the shell 141 to introduce the cold water into the cold water tube array 144, and a cold water outflow outlet 146 disposed on the end or another end of the shell 141 to discharge the cold water from the cold water tube array 144. The cool water inflow inlet 145 may be connected to the cold water inflow passage 52, and the cold water outflow outlet 146 may be connected to the cold water outflow passage 64.

FIG. 4 is a perspective view of a chiller set according to an embodiment. Referring to FIG. 4, a chiller set according to an embodiment may include a plurality of chillers 201 and 202. The plurality of chillers 201 and 202 may be connected in series or parallel. For example, in FIG. 4, the plurality of chillers 201 and 202 are connected to each other in parallel.

The plurality of chillers 201 and 202 may include a first chiller 201 and a second chiller 202. The first and second chillers 201 and 202 may have a same structure as the chiller of FIGS. 2 and 3. The first and second chillers 201 and 202 may have a same capacity and size or may have capacities and sizes different from each other.

Hereinafter, for example, the first and second chillers 201 and 202 may have capacities different from each other. That is, the second chiller 202 may have a capacity greater than a capacity of the first chiller 201.

The first chiller 201 may include a first compressor 210, a first condenser 220, and a first evaporator 240, and the second chiller 202 may include a second compressor 212, a second condenser 222, and a second evaporator 242. The chiller set may further include a cooling water connection tube 260 that connects the first condenser 220 to the second condenser 222, and a cold water connection tube 250 that connects the first evaporator 240 to the second evaporator 242.

The cold water connection tube 250 may function as a path through which the cold water passing through a cold water tube array of the first evaporator 240 may be transferred into the second evaporator 242. More particularly, the cold water passing through the cold water tube array of the first evaporator 240 may be mixed within the cold water connection tube 250, and then, may be introduced into a cold tube array of the second evaporator 242.

The cooling water connection tube 260 may function as a path through which the cooling water passing through a cooling water tube array of the first condenser 220 may be transferred into the second condenser 222. More particularly, the cooling water passing through the cooling water tube array of the first condenser 220 may be mixed within the cooling water connection tube 260, and then, may be introduced into a cold tube array of the second condenser 222.

The first compressor 210, first evaporator 240, and the first condenser 220 may be stacked in a vertical direction with respect to an installation surface of the first chiller 201. The second compressor 212, the second evaporator 242, and the second condenser 222 may be stacked in a vertical direction with respect to an installation surface of the second chiller 200.

Of course, according to kinds of chiller sets, the cold water connection tube 250 and the cooling water connection tube 260 may be omitted.

The chiller set may further include a controller 270 that controls each of the chillers 201 and 202. The controller 270 may input various control commands and display state information of the chillers 201 and 202. The controller 270 may include a memory 272 that stores various information.

Hereinafter, a method of controlling the chiller set according to an embodiment will be described.

FIG. 5 is a flowchart of a method of controlling the chiller set during an initial operation of the chiller set according to an embodiment. FIG. 6 is a flowchart of a method of controlling the chiller set according to a variation in load during operation of the chiller set according to an embodiment. FIG. 7 is a graph illustrating a logarithmic control reference of the chiller according to a head factor and a load factor.

Referring to FIGS. 1, 5, and 7, when an operation starting command of the chiller system is input, the chiller system may operate, in step S1. That is, an operation of the chiller set may start.

When the operation of the chiller set starts, the controller 270 may determine an expected load, in step S2. In step S3, a chiller (or a compressor) to be operated based on the determined expected load may be determined, and in step S4, the determined chiller may be operated.

The expected load may be determined on the basis of a first expected load factor and a first expected head factor. More particularly, the first expected load factor may be detected on the basis of a current cold water inflow temperature detected by the cold water inflow temperature sensor 53 and a target cold water outflow temperature stored in the memory 272.

For example, the first expected load factor may be determined by the following Equation 1.

$\begin{matrix} {\frac{\begin{matrix} {{{Current}\mspace{14mu} {cold}\mspace{14mu} {water}\mspace{14mu} {inflow}\mspace{14mu} {temperature}} -} \\ {{Target}\mspace{14mu} {cold}\mspace{14mu} {water}\mspace{14mu} {outflow}\mspace{14mu} {temperature}} \end{matrix}}{{Cold}\mspace{14mu} {water}\mspace{14mu} {rated}\mspace{14mu} {temperature}\mspace{14mu} {difference}} \times 100\%} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack \end{matrix}$

The cold water rated temperature difference may be a constant stored in the memory 272.

The first expected head factor may be determined on the basis of a current cooling water inflow temperature detected by the cooling water inflow temperature sensor 48 and a target cooling water outflow temperature. For example, the first expected head factor may be determined by the following Equation 2.

$\begin{matrix} {\frac{\begin{matrix} {{{Current}\mspace{14mu} {cold}\mspace{14mu} {water}\mspace{14mu} {inflow}\mspace{14mu} {temperature}} -} \\ {{Target}\mspace{14mu} {cold}\mspace{14mu} {water}\mspace{14mu} {outflow}\mspace{14mu} {temperature}} \end{matrix}}{{Cold}\mspace{14mu} {water}\mspace{14mu} {rated}\mspace{14mu} {temperature}\mspace{14mu} {difference}} \times 100\%} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack \end{matrix}$

The cooling water rated temperature difference, the rated cooling water outflow temperature, and rated cold water outflow temperature may be constants stored in the memory 272. The controller 270 may determine an expected load by comparing the determined first expected load and head factors to the information stored in the memory 272.

Referring to FIG. 7, three ranges for determining the expected load according to the head and load factors during an initial operation of the chiller set may be stored in the memory 272. In FIG. 7, an area left of the dotted line on the left with respect to the two dotted lines may be defined as a first initial range, an area between the two dotted lines may be defined as a second initial range, and an area right of the dotted line on the right may be defined as a third initial range. The dotted line on the left may be a second chiller operation reference line, and the dotted line on the right may be a simultaneous operation reference line of the first and second chillers.

When the first expected load factor and the first expected head factor belong to the first range, the controller 270 may determine the first chiller 201 as a chiller to be operated. When the first expected load factor and the first expected head factor belong to the second range, the controller 270 may determine the second chiller 202 as a chiller to be operated. When the first expected load factor and the first expected head factor belong to the third range, the controller 270 may determine the first and second chillers 201 and 202 as chillers to be operated.

In step S4, the controller 270 may operate the determined chiller (or the compressor). Referring to FIGS. 6 and 7, for example, when an operation of one chiller is determined, one chiller (or the compressor) may operate, in step S11.

In step S12, the controller 270 may determine whether a change in operation method is needed while one chiller operates. To prevent the chiller from being frequently turned on or off due to the load variation, an operation of one chiller may start. Then, after a predetermined time has elapsed, the controller 270 may determine whether a change in operation method is needed. Although embodiments are not limited thereto, the predetermined time may be, for example, one hour. The predetermined time may change according to installation environments or positions of the chiller system.

As the result determined in the step S12, if the change in operation method is needed, the controller 270 may determine a chiller (or a compressor) to be operated, in step S13. In step S14, an operation of the chiller (or the compressor) that is determined to be operated may start. More particularly, the controller 270 may determine an expected load on the basis of a second expected load factor and a second expected head factor, and determine whether a change in operation method is needed, on the basis of the determined expected load.

In this embodiment, the change in operation method may include a case in which the chiller to be operated changes, one chiller additionally operates while one chiller operates, or one chiller is stopped while two chillers operate. For example, the second expected load factor may be determined on the basis of a difference between a current cold water outflow temperature and a target cold water outflow temperature. If the current cold water outflow temperature is greater than the target cold water outflow temperature, the second expected load factor may increase. On the other hand, if the current cold water outflow temperature is less than the target cold water outflow temperature, the second expected load factor may decrease.

The second expected head factor may be determined on the basis of the current cooling water inflow temperature and the target cold water outflow temperature. Alternatively, the second expected head factor may be determined on the basis of a difference between a condensation pressure and an evaporation pressure.

Referring to FIG. 7, five ranges for determining the expected load according to the head and load factors during an operation of the chiller set may be stored in the memory 272. In FIG. 7, an area left of a first load reduction reference line may be defined as a first operation range, an area between the first load reduction reference line and a first load increase reference line may be defined as a second operation range, an area between the first load increase reference line and a second load reduction reference line may be defined as a third operation range, an area between the second load reduction reference line and a second load increase reference line may be defined as a fourth range, and an area right of the second load increase reference line may be defined as a fifth operation range.

For example, while the first chiller 201 operates, when the second expected load factor and the second expected head factor are disposed within the first operation range or the second operation range, the controller 270 may determine that the change in operation method is unnecessary. That is, as the capacity of the chiller module 201 responds to the load, the change in operation method is unnecessary.

Also, while the first chiller 201 operates, when the second expected load factor and the second expected head factor belong to the third operation range, the controller 270 may determine that the change in operation method is unnecessary. That is, as the capacity of the first chiller does not respond to the load, the change in operation method is needed.

Thus, the controller 270 may operate the second chiller 202 having the capacity greater than the capacity of the first chiller 201 and stop the operation of the first chiller 201. More particularly, the controller 270 may perform a starting sequence of the second chiller 202 while the first chiller 201 operates. The starting sequence of the second chiller 202 may include an oil circulation sequence for circulating an oil into the second compressor 212 of the second chiller 202 and a guide vane operation sequence for increasing an opening degree of the guide vane of the second compressor 212.

When the starting sequence of the second chiller 202 is completed, the controller 270 may perform a stopping sequence for stopping the operation of the first chiller 201. After the stopping sequence is performed, the first chiller may be stopped. Of course, the first chiller 201 may be stopped without performing the stopping sequence.

Also, while the second chiller 202 operates, when the second expected load factor and the second expected head factor belong to the fourth operation range, the controller 270 may determine that the change in operation method is unnecessary. That is, as the capacity of the second chiller responds to the load, the change in operation method may be unnecessary.

Also, while the second chiller module 202 operates, when the second expected load factor and the second expected head factor belong to the fifth operation range, the controller 270 may determine that the change in operation method is needed. That is, as the capacity of the second chiller 202 does not respond to the load, the change in operation method may be needed. Thus, the controller 270 may additionally operate the first chiller module 201 while the second chiller 202 operates.

While the first and second chillers 201 and 202 operate at the same time, the second expected load factor and the second expected head factor belong to the fourth operation range, the controller 270 may determine that the change in operation method is needed. That is, as the capacity of the second chiller 202 responds to the load, the change in operation method may be needed. Accordingly, the controller 270 may stop the operation of the first chiller 201.

Also, while the second chiller 202 operates, when the second expected load factor and the second expected head factor belong to the second operation range, the controller 270 may determine that the change in operation method is needed. That is, as the capacity of the first chiller 201 responds to the load, the change in operation method may be needed. Thus, the controller 270 may stop the operation of the second chiller module 202 and operate the first chiller 201.

When it is determined that the operation target changes to the first chiller module 201 while the second chiller module 202 operates, the guide vane of the second compressor 212 of the second chiller 202 may decrease in opening degree. Also, when the opening degree of the guide vane of the second compressor 212 reaches a reference opening degree, a starting sequence of the first chiller 201 may be performed. The starting sequence of the first chiller 201 may be the same as that of the above-described second chiller module 201.

When the starting sequence of the first chiller 201 is completed, the first chiller 201 may normally operate. Also, after the stopping sequence of the second chiller 202 is performed, the second chiller 202 may be stopped. Of course, the second chiller 202 may be stopped without performing the stopping sequence.

According to this embodiment, an operating number control may be realized using the plurality of chillers having capacities different from each other to effectively respond to the load. Also, in this embodiment, the operation method change determination reference when the expected load increases may be different from that when the expected load decreases. This is done to prevent the chiller from being frequently turned on/off.

For example, if the operation method change determination reference when the expected load increases is the same as that when the expected load decreases, that is, if the first load decrease reference line is the same as the second load increase reference line in FIG. 7, when the second expected load factor and the second expected head factor frequently change at a position adjacent to the reference line, the turn-off of the first chiller and turn-on of the second chiller and the turn-off of the second chiller and turn-on of the first chiller may frequently occur. In this case, power consumption may increase, and also, it may be difficult to stably response to the load.

However, according to this embodiment, as the operation method change determination reference when the load increases is different from that when the load decreases, the frequent turn-on/off of the chiller module may be prevented to reduce power consumption and stably respond the load.

Although two chillers form one chiller set in the previous embodiment, embodiments are not limited thereto. For example, at least three chillers may form one chiller set.

Embodiments disclosed herein provide a chiller system.

Embodiments disclosed herein provide a chiller system that may include a plurality of chiller modules or chillers, each of which may include a compressor, a condenser, and an evaporator, and a controller that controls the plurality of chiller modules. The controller may determine an expected load and a chiller module or chiller to be operated of the plurality of chiller modules on the basis of the determined expected load, and operate the determined chiller module.

Embodiments disclosed herein further provide a chiller system that may include a first chiller module or first chiller, including a first compressor; a second chiller module or second chiller including a second compressor having a capacity greater than that of the first chiller module; and a controller that controls the first and second chiller modules. When it is determined that an operation starting command is input, the controller may determine a chiller module to be operated of the first and second chiller modules to operate the determined chiller module.

Embodiments disclosed herein additionally provide a chiller system that may include a first chiller module or first chiller including a first compressor; a second chiller module or second chiller including a second compressor having a capacity greater than that of the first chiller module; and a controller that controls the first and second chiller modules. When it is determined that an operation method change is needed while at least one of the first and second chiller modules operates, the controller may stop the operating chiller module and operate the other chiller module, stop one chiller module while all of the chiller modules operate, or additionally operate the other chiller module while one chiller module operates.

Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.

Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art. 

What is claimed is:
 1. A chiller system, comprising: a plurality of chillers, each of which comprises a compressor, a condenser, and an evaporator; and a controller that controls the plurality of chillers, wherein the controller determines an expected load and a chiller of the plurality of chillers to be operated on the basis of the determined expected load, and operates the determined chiller.
 2. The chiller system according to claim 1, wherein the plurality of chillers have capacities different from each other.
 3. The chiller system according to claim 1, wherein the controller operates a portion or all of the plurality of chillers on the basis of the expected load.
 4. The chiller system according to claim 1, wherein the controller determines the expected load on the basis of an expected load factor and an expected head factor, wherein the expected load factor is determined on the basis of a temperature of cold water introduced into the evaporator and a target cold water outflow temperature, and wherein the expected head factor is determined on the basis of a temperature of cooling water introduced into the condenser and the target cold water outflow temperature.
 5. The chiller system according to claim 1, wherein the plurality of chillers comprise a first chiller, and a second chiller having a capacity greater than a capacity of the first chiller, and when it is determined that an operation method change is needed while one of the first chiller or the second chiller operates, the controller stops the operating chiller and operates the other chiller or simultaneously operates the first and second chillers.
 6. The chiller system according to claim 5, wherein the controller determines an expected load to determine whether an operation method change is needed according to the expected load.
 7. The chiller system according to claim 6, wherein a determination reference for determining whether the operation method change is needed comprises a determination reference when the expected load increases and a determination reference when the expected load decreases.
 8. The chiller system according to claim 6, wherein the controller determines the expected load on the basis of an expected load factor and an expected head factor, wherein the expected load factor is determined on the basis of a temperature of cold water discharged from the evaporator and a target cold water outflow temperature, and wherein the expected head factor is determined on the basis of a temperature of cooling water introduced into the condenser and the target cold water outflow temperature.
 9. The chiller system according to claim 5, wherein, if it is determined that the chiller to be operated changes to the second chiller while the first chiller operates, the controller performs a starting sequence of the second chiller and stops the operation of the first chiller after the starting sequence of the second chiller is completed.
 10. The chiller system according to claim 5, wherein, if it is determined that the chiller to be operated changes to the first chiller while the second chiller operates, the controller reduces an opening degree of a guide vane of the compressor of the second chiller and performs a starting sequence of the first chiller when the opening degree of the guide vane reaches a reference opening degree.
 11. The chiller system according to claim 10, wherein the controller stops the operation of the second chiller after the starting sequence of the first chiller is completed.
 12. A chiller system, comprising: a first chiller comprising a first compressor; a second chiller comprising a second compressor having a capacity greater than a capacity of the first compressor; and a controller to control the first and second chillers, wherein, when it is determined that an operation starting command is input, the controller determines a chiller to be operated of the first and second chillers and operates the determined chiller.
 13. The chiller system according to claim 12, wherein, when it is determined that an operation method change is needed while one chiller of the first and second chillers operates, the controller stops the operating chiller and operates the other chiller or simultaneously operates the first and second chillers.
 14. The chiller system according to claim 12, wherein, when it is determined that the operation method change is needed while the first and second chillers operate at the same time, the controller stops the first chiller or the second chiller.
 15. A chiller system, comprising: a first chiller comprising a first compressor; a second chiller comprising a second compressor having a capacity greater than a capacity of the first compressor; and a controller to control the first and second chillers, wherein, when it is determined that an operation method change is needed while at least one of the first chiller or the second chiller operates, the controller stops the operating chiller and operates the other chiller, or stops one chiller module while all of the chillers operate, or additionally operates the other chiller while the one chiller operates.
 16. The chiller system according to claim 15, wherein, if it is determined that the chiller to be operated changes to the second chiller while the first chiller operates, the controller performs a starting sequence of the second chiller and stops the operation of the first chiller after the starting sequence of the second chiller is completed.
 17. The chiller system according to claim 15, wherein, if it is determined that the chiller to be operated changes to the first chiller while the second chiller operates, the controller reduce an opening degree of a guide vane of the second compressor and performs a starting sequence of the first chiller when the opening degree of the guide vane reaches a reference opening degree.
 18. The chiller system according to claim 17, wherein the controller stops the operation of the second chiller after the starting sequence of the first chiller is completed.
 19. The chiller system according to claim 17, wherein the controller determines the expected load to determine whether an operation method change is needed according to the expected load.
 20. The chiller system according to claim 19, wherein a determination reference for determining whether the operation method change is needed comprises a determination reference when the expected load increases and a determination reference when the expected load decreases.
 21. A chiller system, comprising: a plurality of chillers, each of which comprises a compressor, a condenser, and an evaporator; and a controller that controls the plurality of chillers, wherein the controller determines an expected load and a chiller or chillers of the plurality of chillers to be operated on the basis of the determined expected load, and operates the determined chiller or chillers, wherein the controller determines the expected load on the basis of an expected load factor and an expected head factor of an operating chiller, wherein the expected load factor is determined on the basis of a temperature of cold water introduced into the evaporator of the operating chiller and a target cold water outflow temperature, and wherein the expected head factor is determined on the basis of a temperature of cooling water introduced into the condenser of the operating chiller and the target cold water outflow temperature.
 22. The chiller system according to claim 21, wherein the plurality of chillers have capacities different from each other.
 23. The chiller system according to claim 21, wherein the plurality of chillers comprise a first chiller, and a second chiller having a capacity greater than a capacity of the first chiller, and when it is determined that an operation method change is needed while one of the first chiller or the second chiller operates, the controller stops the operating chiller and operates the other chiller or simultaneously operates the first and second chillers.
 24. The chiller system according to claim 23, wherein the controller determines the expected load of the operating chiller to determine whether an operation method change is needed according to the expected load of the operating chiller.
 25. The chiller system according to claim 24, wherein a determination reference for determining whether the operation method change is needed comprises a determination reference when the expected load of the operating chiller increases and a determination reference when the expected load of the operating chiller decreases.
 26. The chiller system according to claim 23, wherein, if it is determined that the chiller to be operated changes to the second chiller while the first chiller operates, the controller performs a starting sequence of the second chiller and stops the operation of the first chiller after the starting sequence of the second chiller is completed.
 27. The chiller system according to claim 23, wherein, if it is determined that the chiller to be operated changes to the first chiller while the second chiller operates, the controller reduces an opening degree of a guide vane of the compressor of the second chiller and performs a starting sequence of the first chiller when the opening degree of the guide vane reaches a reference opening degree.
 28. The chiller system according to claim 27, wherein the controller stops the operation of the second chiller after the starting sequence of the first chiller is completed. 